Free Engineering Tool
PCB Conductor Spacing & Voltage Calculator
Look up the minimum clearance between PCB conductors for a given voltage — or find the maximum voltage for a given spacing. Based on IPC-2221B Table 6-1, the industry standard for electrical conductor spacing.
Conductor Spacing Calculator
Enter voltage to find minimum spacing, or enter spacing to find maximum voltage. Use DC or peak AC voltage.
Design Inputs
DC or peak AC voltage between conductors
Results
Minimum Spacing (B2)
at 100 V DC/peak
All Categories
| B1 | 0.1 mm | 3.9 mil |
| B2 | 0.6 mm | 23.6 mil |
| B4 | 0.13 mm | 5.1 mil |
Per IPC-2221B Table 6-1. Use DC or peak AC voltage. Altitude, humidity, contamination and transient overvoltages may require additional derating. For safety-critical or high-voltage designs, consult UL/IEC 60950/62368 and your safety agency.
Reference
IPC-2221B Table 6-1: Minimum Spacing (mm)
Abbreviated reference. B1 = internal conductors; B2 = external, uncoated, sea level to 3050 m; B4 = external, with permanent polymer coating. For the full table including B3 and B5, refer to IPC-2221B.
| Voltage (V DC/peak) | B1 Internal | B2 External | B4 Coated |
|---|---|---|---|
| 0–15 | 0.05 | 0.10 | 0.05 |
| 16–30 | 0.05 | 0.10 | 0.05 |
| 31–50 | 0.10 | 0.60 | 0.13 |
| 51–100 | 0.10 | 0.60 | 0.13 |
| 101–150 | 0.20 | 0.60 | 0.40 |
| 151–170 | 0.20 | 1.25 | 0.40 |
| 171–250 | 0.20 | 1.25 | 0.40 |
| 251–300 | 0.20 | 1.25 | 0.40 |
| 301–500 | 0.25 | 2.50 | 0.80 |
| >500 | 0.0025/V | 0.005/V | 0.00305/V |
Source: IPC-2221B, Table 6-1 "Electrical Conductor Spacing". Above 500V, add the stated mm/V factor for every additional volt. For safety-critical or UL-certified designs, also consult IEC 60950-1 / IEC 62368-1 creepage and clearance tables.
FAQ
Conductor spacing, answered
What is the minimum spacing between PCB conductors?
Per IPC-2221B Table 6-1, for external uncoated conductors at sea level: 0.1 mm for 0–30V, 0.6 mm for 31–150V, 1.25 mm for 151–300V, and 2.5 mm for 301–500V. Internal conductors can be closer due to insulating dielectric.
What is IPC-2221B Table 6-1?
Table 6-1 in IPC-2221B specifies minimum electrical spacing between conductors to prevent voltage breakdown and arcing. It covers internal conductors (B1), external uncoated at various altitudes (B2, B3), and external with coatings (B4, B5).
Does conformal coating reduce required spacing?
Yes. A permanent polymer coating (category B4) allows reduced spacing. At 100V: uncoated external (B2) needs 0.6 mm, while coated (B4) needs only 0.13 mm.
Should I use DC or AC voltage?
Use the peak voltage. For DC, use directly. For AC, use V_rms × √2. Account for transients and overshoot above steady-state voltage.
Are these spacing rules sufficient for safety certification?
IPC-2221B is a design standard, not a safety standard. For UL/CE certification, also meet IEC 60950-1 or IEC 62368-1 creepage/clearance requirements, which may be more stringent depending on pollution degree and insulation type.
Design meets manufacturing
High-voltage boards with correct clearances, IPC Class 2 & 3, engineer-reviewed before fabrication. 1-piece MOQ.